Systems and methods for improving the efficiency of a combined cycle power plant

Abstract

Systems and methods for improving the efficiency of a power generation facility utilize heat energy to preheat inlet-air that is supplied to the compressor of a turbine or to preheat fuel that is burned in the turbine. The heat energy used to preheat the inlet-air can be drawn from a heat recovery steam generator (HRSG) that produces steam using at least part of the exhaust gas of the turbine. The heat energy can be obtained from one or more predetermined points within the HRSG, such as a feed water line exiting a drum of the HRSG or a feed line connecting an economizer of the HRSG to a drum of the HRSG. The fluid drawn from the predetermined point passes through a heat exchanger or a preheater to remove the heat energy used for preheating. The fluid is then returned to the HRSG immediately downstream from the point from which it was drawn.

Description

BACKGROUND OF THE INVENTION[0001]The invention relates to systems and methods for improving the efficiency of a power generating facility that utilizes a turbine.[0002]Turbomachines, such as gas turbines, aero-derivatives, or the like, commonly operate in a combined-cycle and / or cogeneration mode. In combined-cycle operation, a gas turbine is connected to a generator that produces electricity. A heat recovery steam generator (HRSG) receives at least a portion of the exhaust gas produced by the gas turbine, and the HRSG uses the heat energy in the exhaust gas to generate steam. The steam produced by the HRSG flows to a steam turbine connected to another generator which produces additional electricity. In a co-generation operation, a portion of the steam generated by the HRSG is sent to a separate process requiring the steam.[0003]Combined-cycle and cogeneration plants are rated to generate the maximum amount of energy (mechanical, electrical, etc) at minimum fuel consumption while op...

AI Technical Summary

Benefits of technology

[0008]In one aspect, the invention can be embodied in a system for improving the efficiency of a power generation facility. The system includes a turbine comprising a compressor which receives inlet-air, a combustion system and a turbine section, wherein the turbine produces an exhaust-gas. The system also includes a heat recovery steam generator (HRSG) which receives a portion of the exhaust-gas and produces steam. The system also includes a preheater that obtains heat energy from the HRSG and that uses that heat energy to improve the efficiency of the power generation facility, wherein the heat energy obtained from the HRSG is obtained from a fluid drawn from a predetermined point within the HRSG, and wherein after heat energy has been extracted from the fluid, the fluid is returned to the HRSG at the predetermined point.

[0009]In another aspect, the invention can be embodied in a method of improving the efficiency of a power generation facility that includes a turbine having a compressor which receives inlet-air, a combustion system and a turbine section, the turbine producing an exhaust-gas that is at least partially provided to a heat recovery steam generator (HRSG). The method includes drawing fluid from a predetermined point within the HRSG, obtaining heat energy from the fluid, using the obtained heat energy to improve the efficiency of the power generation facility, and returning the fluid to the predetermined point within the HRSG after heat energy has been obtained from the fluid.

Problems solved by technology

Base load operations, although desired by operators, is not always feasible.

There may not be a demand in the energy market (electrical grid, or the like) for all of the energy generated at base load.

A gas turbine operating at part load may not maintain emissions compliance if it is running below a particular load point.

Further, any retrofit changes should not increase operation or maintenance costs, otherwise the retrofit changes may not be economically worthwhile.

Otherwise the improvements in efficiency and / or turndown range may be outweighed by higher operating or maintenance costs, or reduced efficiency during other operating conditions.

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